Need Help Finishing Slabs

[coinking]

Hello, folks! I found a very good website with instructions for hand finishing rocks, and it has worked like a charm so far...using 6" sanding disks progressively from 80 to 600 grit. Still have some very fine scratches, which the article says to take out with jeweler's rouge, but it isn't removing the scratches! Could sure use some help on how to get a mirror finish on these fine stones. I have tried various polishing tips, including leather, with my Dremel tool. If anyone knows how to complete the process, I'm sure it's the good people on Treasure Net. Thanks!

 

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[rmptr]

Hi Coin,
Obviously you are going to need something coarser than the jewelers rouge...
... and finer than the 600!

Try google lapidary supply for one you like...

They have diamond powder and diamond spray... both in little bottles about $20ea.

There are also finer grits of Si carbide and diamond on sheets, belts, and disks.

Cerium oxide also used for polishing.

Good luck,
rmptr

 

[coinking]

OK then, I'm heading in the right direction...just ordered 1200 grit diamond paste from Eloxite Corp., who I have been working with for several years. (Fantastic selection and outstanding customer service!) I knew that one of the more knowledgeable members could help! What would be the best way to use the paste, I have a felt wheel for the grinder, or leather wheels for my Dremel.

 

[rmptr]

Oh gosh, Coin...

I'm far from an expert!

Trying to learn about lapidary myself...

Good luck with your project.

rmptr

 

[MEinWV]

A first consideration for me would be the material itself. Softer stone such as Malachite, Fluorite, Turquoise, or Howlite are easier to polish by hand. When you get into the agates it is harder to work. Try to choose slabs that are as smooth as possible. Many slabs have a small lump of extra material on the end as it leaves the saw. Trim that off before you begin. I find that the extra time taken on the first sanding is the key to a smooth finish. I use many grits of wet or dry sandpaper. If you only use a few grits you may not get out the fine scratches that effect the final polish. You need to use a superflat piece of stable material such as aluminum or hard resin. This is placed in a pan of water such as a litter box. Change the water with each grit but don't pour it down your sink drain, for obvious reasons. That first sanding must take the material down to a even surface. This first stage may take longer but it is crucial to the end result. I will take it all the way down to 2000 grit wet or dry. By this time the slab is already taking on a good polish. I then take the pre-polish and final polish that you use for tumblers and use them on hard felt and leather pads. Just keep the polishes and pads separate from each other and always rinse the slab well before changing to finer grits.

Hope you get some good ideas from this! Good Luck!

 

[coinking]

Dear Mr. WV, thanks so much for your tips on polishing, but I still have a couple of specific questions, should you have the time to answer. I understand your need for a completely level surface, since I have discovered on a couple of my slabs the outside edges are being polished, while the slightly convex inner surface is not. How can I "level" my slab? You also mentioned hard buffing wheels with prepolish and polish stages...how do you apply the polish? I have been thinking of mixing up a bit with water, but I assume direct application to the wheel would cause much of it so spin off. Do you apply to the face of the slab itself? Is there a drying period? I greatly appreciate your previous answers, and look forward to any future replies eagerly!!

 

[MEinWV]

Sorry for not responding sooner! I have tried twice already, but it keeps telling me my time has expired and I lose what I have written. I will try again soon.

 

[coinking]

Sorry for not responding sooner! I have tried twice already, but it keeps telling me my time has expired and I lose what I have written. I will try again soon.

Thanks so much for your efforts!! I look forward to hearing from you once that annoying problem is resolved.

 

[pronghorn]

Hello, folks! I found a very good website with instructions for hand finishing rocks, and it has worked like a charm so far...using 6" sanding disks progressively from 80 to 600 grit. Still have some very fine scratches, which the article says to take out with jeweler's rouge, but it isn't removing the scratches! Could sure use some help on how to get a mirror finish on these fine stones. I have tried various polishing tips, including leather, with my Dremel tool. If anyone knows how to complete the process, I'm sure it's the good people on Treasure Net. Thanks!

I would be interested in knowing the website you speak of if you could post a link.
I hope to polish some of the tons of petrified wood I have. I have never polished
anything other than the chair in front of this computer and need a step by step
course starting at the very beginning. Thank you.

 

[Nashoba]

Hello, folks! I found a very good website with instructions for hand finishing rocks, and it has worked like a charm so far...using 6" sanding disks progressively from 80 to 600 grit. Still have some very fine scratches, which the article says to take out with jeweler's rouge, but it isn't removing the scratches! Could sure use some help on how to get a mirror finish on these fine stones. I have tried various polishing tips, including leather, with my Dremel tool. If anyone knows how to complete the process, I'm sure it's the good people on Treasure Net. Thanks!

I would be interested in knowing the website you speak of if you could post a link.
I hope to polish some of the tons of petrified wood I have. I have never polished
anything other than the chair in front of this computer and need a step by step
course starting at the very beginning. Thank you.

Get ready to buy some equipment and spend some bucks. My suggestion is for you to take your time and try to pick up used pieces of quality equipment to save some dinero. Some petrified wood is very hard, but when she is cut and polished she can be beautiful beyond words. You may want to look into the making of cabachons as well. I know there are some pieces you have in those pics that I would kill to have a few slabs for cabbing.
Defintiely some sweet material you have out there!

~Nash~

 

[coinking]

Dear Pronghorn, here's the link: http://rocktumblingsupplies.com/polishing_rocks_by_hand.phtml. I'm still having a bit of a problem with the prepolish and polish stages, since I am uncertain how to apply them without having them go flying off onto my goggles and clothing. The nice gentleman from WV was going to supply additional information, but we'll have to wait until his email issues are resolved.

 

[MEinWV]

OK! I'm back! I hope this works!

Are you using sanding disks on an electric drill or bench grinder? If you are then I am not sure that you can get a even surface on the slab.

The first step in the sanding operation is to get that even surface. This step will take the longest time but is the most important one in order for the rest of the steps to work. Use a shallow pan with water. A piece of aluminum about 10"x10"x3/8" thick will work good as an even base. Place in pan of water and put a sheet of 80 grit "wet or dry" sandpaper on the aluminum base. Take the slab and place it on the sandpaper. With normal hand pressure use circular motions and keep checking the slab. If the slab is fairly smooth to begin with it won't be long before you get an even surface. In order to work through the finer grits, that first sanding is the most important. If the slab is too rough, it might be better to get another slab. Nash is right about petrified wood being very hard. It may not be suited for hand grinding.

The pre polish and polish is also done by hand, and ......Yes, I make a slurry of powder and water and place it on the suede leather pad. Keep it wet and do the same circular motions. Rinse the slab between each grit and polishes. Use separate pads for each polish. The hard felt wheel I mentioned is an old one and I don't know if they are still available, but I didn't use it on a machine, I just used it as a flat polishing base as it is felt that is glued to a piece of marine plywood.

Good luck!

 

[coinking]

Dear Mr. WV, just what I needed!! Yes, I am using 6" disks on a flat aluminum piece at the other end of my rock saw. Having one heck of a time getting a couple of them even, so I'm just keeping at it. Several more are ready for pre-polish and polish stages. Also have a suede leather disk, and a felt disk, so I can use one for each stage. Used my extensive dental work to come up with a neat trick I'd like to share...bought some carbon paper, and put the face of the slab down on it and move in circles. It marks the areas that are too high, and then I grind them with a Dremel stone. (Similar to what the dentist does after fitting a crown. You know - "bite down and grind" and "tap, tap, tap" on the little piece of carbon paper?) This keeps me from burning through my 80 grit disks quite so fast. I have some really fabulous thundereggs bought at an estate sale, and I'll post some pics when they're done. About 80 years ago, someone decided to "fix" them with varnish, believe it or not! I really appreciate now your comment about the first stage being so important. If they're not perfectly flat, you're really not going to be happy with the end product! Thanks so much for battling through the reply troubles!!!!! (You wouldn't believe how much I was looking forward to your reply.)

 

[MEinWV]

Glad I could help! As I was searching on line for hand polishing of slabs and gems I found something about making your own equipment.

Do a search(homemade lapidary equipment) to see if you can find a site like that. They had plans for making a flat lap for polishing slabs and geode halves. You might be able to make one for very little cash that will help speed things up for you. I have several pieces of equipment that are in storage right now. I would love to get started cutting and polishing again. I have a Lortone saw and cabbing combo with the aluminum disk on the end, maybe like the one you have, but have never tried to polish slabs on it, just cabochon stones.

Good luck & hope to hear of your progress soon, and maybe even some pics!

 

[greydigger]

Am not sure if this will help, but you were talking about "Flatness".
Been a tool&die maker for 25 yrs. and have a "Tombstone" - flat granite plate to measure things on. Flatness measured by optics is .00005" per sq'.
Cost a bunch. A neighbor company made granite tombstones and other things
and had a sale of unwanted slabs. I got a couple 12'X12" for $5 each.
sweeping a .0001" indicator around them they were within .0005" of flatness.
Prussian Blue on the workpiece rubbed away will show you the high spots.
I always used felt bobs with my dremel and fine diamond to take them down.
This was Hardened Toolsteel so am not sure of rocks but the idea should be the same. Start coarse, work finer.

 

[coinking]

Am not sure if this will help, but you were talking about "Flatness".
Been a tool&die maker for 25 yrs. and have a "Tombstone" - flat granite plate to measure things on. Flatness measured by optics is .00005" per sq'.
Cost a bunch. A neighbor company made granite tombstones and other things
and had a sale of unwanted slabs. I got a couple 12'X12" for $5 each.
sweeping a .0001" indicator around them they were within .0005" of flatness.
Prussian Blue on the workpiece rubbed away will show you the high spots.
I always used felt bobs with my dremel and fine diamond to take them down.
This was Hardened Toolsteel so am not sure of rocks but the idea should be the same. Start coarse, work finer.

Dear Grey, great idea!! I have a slab of polished granite for leather working that should work.